Researchers say a Montana copper operation released arsenic and lead that spread across much of North America and reached the Arctic, according to a study published Nov. 10 in Nature Sustainability.
The international team analyzed 10 ice cores from Greenland, the Russian Arctic and northern Canada. Particles deposited in the ice preserve a record of past air pollution. The cores showed that toxic metal levels rose sharply from about 1886 to 1918, reaching roughly 15 times their earlier levels.
Atmospheric models, metal measurements and historical production records pointed to the Anaconda Copper Mine complex near Butte as the main source. The researchers estimate that during peak production, the operation emitted about 10,000 metric tons of arsenic and 4,000 metric tons of lead each year. The researchers compared modeled pollution levels with census data from the early 1900s.
They estimated that about 50.5 million Americans and 600,000 Canadians lived in areas where arsenic levels were above 1 nanogram per cubic meter. The study estimates past exposure. It does not establish that particular people became ill because of the pollution.
The findings show that ice records and atmospheric models can help identify how far historic industrial pollution spread.